In this unit analogy question, select the related word from the given alternatives: Length : Meter :: Power : ?

Introduction / Context:
Analogy questions involving scientific units test your understanding of which physical quantities are measured by which standard units. Here the pair Length and Meter is given, and you must identify the correct unit that stands in the same relationship to Power. This type of question is common in general aptitude and basic science segments of competitive examinations.

Given Data / Assumptions:
- Length is a physical quantity that describes how long something is.
- Meter is the standard SI unit used to measure length.
- Power is another physical quantity related to the rate of doing work or using energy.
- The options for the unit of power are Calories, Degree, Watt, and Kilogram.
- We assume standard SI definitions and common scientific usage.

Concept / Approach:
The concept is to match the given quantity with its correct standard unit. Length and meter form a correct pair of quantity and unit. In the same way, we must recall which unit is used for power in the SI system. Power is defined as work done per unit time or energy transferred per unit time, and its SI unit is watt. This simple recall question becomes an analogy question by presenting the pattern Quantity : Unit :: Quantity : Unit.

Step-by-Step Solution:
Step 1: Recognize that the first pair, Length : Meter, is a quantity to unit relationship.Step 2: Recall that Power is the rate of doing work or the rate of energy transfer.Step 3: From basic physics, the SI unit of power is watt, commonly written with the symbol W.Step 4: Check each option: Calories measure energy, Degree usually measures temperature or angles, Watt measures power, and Kilogram measures mass.Step 5: Only Watt matches Power in the same way Meter matches Length, so Watt is the correct answer.

Verification / Alternative check:
You can quickly verify the match by writing small example statements. For length you can say, the length of the room is 5 meters. For power you can say, the power of the motor is 500 watts. Trying to use other options in similar sentences shows they do not fit. Saying the power is 500 kilograms or 500 degrees is scientifically incorrect. This simple language based check confirms that watt is the valid unit of power.

Why Other Options Are Wrong:
- Calories: This unit measures energy, not power. It may appear related, but power involves energy per unit time, not energy alone.
- Degree: Degree commonly measures temperature or angles, for example degree Celsius or degree of rotation, not power.
- Kilogram: This is the SI unit of mass, describing how much matter is in an object, and has no direct unit relationship with power.

Common Pitfalls:
Some students confuse energy and power and may select Calories because they remember power and energy appear together in physics formulas. Others are distracted by familiar units like Degree or Kilogram without checking what they actually measure. To avoid such errors, always recall the fundamental definition of the quantity and the SI unit attached to it. A quick mental review of basic physics quantities and units can dramatically improve performance on such analogy items.

Final Answer:
Just as Meter is the unit of Length, Watt is the standard unit of Power, so the correct completion of the analogy is Power : Watt.